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Small-scale desalination process shows promise

Energy-intensive
desalination processes may be a thing of the past. A new method developed by
chemists from The University of Texas (Austin) and the University of Marburg
(Germany) requires such a small amount of energy that it can run on a
store-bought battery, according to a news release from The University of Texas.

The
electrochemically mediated seawater desalination process eliminates the need
for a membrane and separates salt from water at a microscale. This makes the
process less complex and less energy-intensive than other conventional
techniques, the news release says.

The
process takes place inside a plastic chip that contains a microchannel with two
branches. For desalination, 3.0 volts are applied to the plastic chip filled
with seawater. At the junction of the channel, an embedded electrode
neutralizes some of the chloride ions in seawater to create an ion-depletion
zone that increases the local electric field compared to the rest of the
channel. This change in the electric field redirects salt into one branch and
allows desalinated water to pass through the other branch, the news release
says.

Currently
the microchannels are about the size of a human hair and produce about 40
nL/min of desalinized water. One challenge is scaling up the process, but the
researchers are confident that this can be achieved too, the news release says.

With the
system, the research team has achieved 25% desalination. While drinking water
requires 59% desalination, the researchers believe the system can achieve this,
the news release says.

The
patent-pending process, which is in commercial development by Okeanos
Technologies (Union, Ky.), has been described in the journal, Angewandte
Chemie.

Conventional
water quality tests that measure the overall levels of Escherichia coli may
not be as accurate as originally thought, according to a study from University
at Buffalo (N.Y.) and Mercyhurst University (Erie, Pa.). With the assistance of
the Shiga toxin, E. coli may fend off aquatic predators and survive
longer in waterways, according to a University at Buffalo news release.

The
study, published in the Applied and Environmental Microbiology journal,
suggests that measuring overall E. coli in waterways may be a poor way
to find out if water poses a danger to swimmers.

Strains
of E. coli that produce the Shiga toxin are harmful to humans. And these
strains also persist longer in water than other strains because the toxin helps
E. coli resist predation by bacterial grazers, explained Gerald
Koudelka, University at Buffalo professor of biological sciences who led the
study.

Researchers
placed several different strains of E. coli into the water samples from
Presque Isle State Park and Mill Creek Stream in northern Pennsylvania to test
how Shiga affects its survival. Water contained protists that feed on E.
coli. The toxin producers fared better against grazing protists than the
toxin-free E. coli strains, with less reduction in numbers and
persisting longer in water, the news release says.

Conventional water quality testing could inaccurately predict the safety
of waterways. Because waterways with low levels of Shiga-producing E. coli
still can harm human health, showing safe levels of E. coli may
underestimate the danger. And conversely, waterways with high levels of
non-Shiga-producing E. coli may be closed but actually be safe for recreation,
the news release says.

“You
could have high E. coli populations in a lake, but absolutely no
[Shiga-producing E. coli],” Koudelka said in the news release. “This is
the economic part of it: It’s a problem because you might have a beach that’s
closed for days even though it’s safe.”

Water
infrastructure financing explained in new report

The facts behind
financing drinking water infrastructure are revealed in a new report released
by American Rivers (Washington, D.C.). The report, “Drinking Water
Infrastructure: Who Pays and How,” covers the sources for and risks
accompanying financing water infrastructure, information on rate structure, and
conservation efforts and analysis.

The report includes
current information designed to help those advocating for clean water and
infrastructure projects understand how water utilities finance new projects,
according to an American Rivers news release.

“This guide is an
essential resource for advocates working in their communities to ensure that
water is provided equitably and sustainably, for present and future generations,”
said Sharlene Leurig, senior manager with the Ceres Water Program (Boston), in
the release.

Mussels equipped with backpacks retrieve water-quality data

Anton
Kruger has a special place in his heart for a filter-feeder, the freshwater
mussel. Kruger, a University of Iowa (Des Moines) IIHR—Hydroscience &
Engineering associate research engineer and associate professor of electrical
and computer engineering, has been named Donald E. Bently Faculty Fellow in
Engineering. This recognizes his commitment to students and research. One of
these ongoing research projects involves using river mussels as water-quality
sensors, according to a university blog.

Kruger is
leading a water-quality research project where each mussel is equipped with a
“backpack” of electronic sensors to regularly and remotely transmit data, the
blog says. This will create a network of sensor-collecting data about the
nitrogen cycle in waterways. The wireless backpack — designed by university
electrical engineering student, Hannah Taylor — contains a small radio and
sensors that measure nitrogen in water.

“They
actually filter the amount of water that a major city, like Minneapolis,
consumes on a daily basis,” Kruger said in the blog. “I am captivated with the
idea of getting a backpack on a mussel.”

The
mussel chosen for the project is the larger, pocketbook mussel species, so the
backpack does not restrict the mussel’s movement and behavior. Currently the
backpack-wearing mussels are in a laboratory microhabitat that pumps in fresh
river water and has lights that create artificial day and night cycles. The
researchers plan to release these mussels back into the Iowa River to collect
data, the blog says.

Kruger’s
team is working to make the sensors inexpensive so they could be disposable and
to develop batteries with a longer lifespan for the backpacks. They hope to
gather data from 5 years or more, the blog says.